Theoretical Study of the Release and Consumption of an Agent in Food from Active Polymer Packaging

Abstract

The role of packaging has been extended from passive protection to an active role in improving food quality. Active packaging works with the food to produce a desired effect. Often, micro-organism growth causes food spoilage, so active packaging allows for the controlled release of an anti-microbial agent into the food. Thus, packaging is made of two layers, at least, one with an impermeable polymer protecting the system from the environment, and the other with a polymer carrier containing the agent, the polymer carrier being bound to the inside of the packaging and in contact with the food. This study is undertaken in order to describe the process of the agent release. The agent diffuses through the polymer carrier with a constant diffusivity into the liquid food, with a finite coefficient of convective transfer at the interface. Because of the high convective effect in the liquid, the concentration of the agent in the liquid food is uniform. Moreover, the rate of consumption of the agent resulting from its action on the micro-organisms is controlled by a first-order reaction with respect to its concentration in the liquid. The results are expressed in terms of the profiles of concentration of the agent developed through the thickness of the polymer carrier, the kinetics of the agent remaining free in the liquid, and the kinetics of consumption of the anti-microbial agent by the microorganisms. Two new dimensionless numbers are introduced, taking into account the rate of consumption of the agent and either the diffusivity, when the process is controlled by diffusion, or the rate of convection coefficient when it is controlled by convection, in order to clarify the process an help those who are not specialists in modelling.

Diffusivity of propolis compounds in Polylactic acid polymer for the development of anti-microbial packaging films

“…Although its potentialities, propolis has not been explored yet for anti-microbial food packaging applications, so research and development of its incorporation in food packaging materials is needed. Mathematical modeling of mass transfer is necessary to in-depth understanding and optimization of such propolis delivery system, as it has been already done for drug release systems (Charlier et al, 2000;Siepmann and Peppas, 2001) or for other active packaging (Buonocore et al, 2003;El Kouali et al, 2003). Most of the mathematical models used for modeling the release kinetics are based on analytical solutions of the Fick's second law given for restrictive conditions of geometry and specific boundary conditions.…”

Problems of food protection by polymer packages

“…1 Moreover, two new dimensionless numbers have been introduced, the number of Savoie in the first case and the number of Moû -tiers in the second case. 12 A problem appears with the various qualifications of the specialists necessitated by the work. There should be the specialists in polymers and polymer additives, the people responsible for the food, the experts in packaging, but also the bacteriologists as well as the analysts.…”

“…14 The kinetics of release of the agent in the food and the kinetics of the agent remaining free can be obtained by using a numerical model. 1,12 Depending on the value of the dimensionless number R, two cases have been considered: for R larger than 50-100, the process is controlled mainly by diffusion, and for R lower than 5-10, the process is controlled by convection. 1 Moreover, two new dimensionless numbers have been introduced, the number of Savoie in the first case and the number of Moû -tiers in the second case.…”

“…1,[7][8][9] The function of the active packages is shortly considered, when the package is able to release an antibacterial agent, 10,11 and an example of kinetics is given. 12 Finally, an attempt is made in order to describe the operational conditions necessary for predicting a standardised test and apparatus, which should be used by everybody working in the field of food pollution. On the other hand, the best equation leading to the safer results is drawn so that the results of these experiments could be expressed in valuable data.…”

Food preservative content reduction by controlling sorbic acid release from a superficial coating

“…Mathematical modelling of mass transfer is necessary to the in-dept understanding and optimizing of such active edible coating as it has been already done for drug release system (Charlier, Leclerc & Couarraze, 2000;Siepmann & Peppas 2001) or non non-edible active packaging (Buonocore, Del Nobile, Panizza, Corbo & Nicolais, 2003;El Kouali, Salouhi, Labidi, El Brouzi & Vergnaud, 2003).…”